The present disclosure generally relates to electric power systems and determining disturbance location in electric power systems.
Electric power systems, also known as power grids, typically include generators, transmission lines, and loads, among other electrical components. Although power grids are relatively robust systems under most operating conditions, various kinds of disturbances may impact their reliability. If power grids are not properly monitored, protected, and/or controlled, some of these disturbances may cause failures and eventually lead to blackouts. Quickly and accurately determining the locations of disturbances in power grids may improve operators' situational awareness of the power grids. Informed of the location of a disturbance, operators may better implement remedy plans to mitigate the impact of the disturbance and restore the system to a secure state.
Recent developments in synchrophasor measurement technology and wide-area measurement systems (WAMS) have provided an advanced platform for locating disturbances. In WAMS, phasor measurement units (PMUs) monitor system voltage and current phasors using high-precision synchronized time information, thus capturing fast dynamics of system states, which may be used for disturbance analyses. Existing methods that use PMU data to locate disturbances usually include two steps-determining arrival times of a plurality of PMUs to a disturbance and then estimating the location of the disturbance.
Most of the existing methods determine arrival times of PMUs as times at which frequency measurements at the PMUs exceed a threshold. These methods require setting a frequency threshold f to track the frequency change Δf. However, since frequency is the integral of the generation-load imbalance caused by a disturbance (i.e.,
            Δ      ⁢                          ⁢      f        =                  ∫                  t          0                          t          1                    ⁢                                                                  P                m                            ⁡                              (                t                )                                      -                                          P                e                            ⁡                              (                t                )                                                          2            ⁢                                                  ⁢            H                          ⁢        d        ⁢                                  ⁢        t              ,where H is the inertia constant of the system), the determined arrival times may be very sensitive to the setting of the frequency threshold f. A frequency threshold f that is too small may make the arrival times vulnerable to noise. A frequency threshold f that is too large may produce incorrect arrival times due to system oscillation, since frequency profiles may cross over one another in oscillations.
To estimate the disturbance location, the methods then typically employ a least-square disturbance location approach, with the assumption that the propagation speed of an electromechanical wave, which is generated by the disturbance and which propagates outwards from the disturbance location, is constant throughout the power grid. In fact, the propagation speed varies widely throughout the power grid due to system conditions such as unit commitment and load dynamics, thus making it difficult to apply these methods in practice to locate the disturbance location.
Other methods combine measurements with power grid models to locate generator trips. However, these methods rely on the power grid models in calculating the propagation distance, and thus cannot be applied when the grid models are not available or the system topologies change with operation conditions.
Therefore, the inventors recognized a need in the art for systems and methods for accurately and reliably determining the location of a disturbance in an electric power system.